How noisy are iMacs and Mac Pros?

I'm planning on re-entering the Mac world early next year. I'm either going to go for a high end iMac (24") or a low end Mac Pro. The main decider will be the price and my available cash.

One issue that concerns me is noise. In short, how loud are the various machines? My current PC sits there making a noise like a small turbine and I really want something as near-silent as possible as a replacement.

The MP is very silent, depends on the drives you choose, the seagates are silent, especially entreprise class drives.
The fans turn on when the computer is doing intensive tasks, like rendering. But even in that case the noise is low.
The imac is silent to, not like a MB(P) but silent.

Both the iMac and the Mac Pro are very quiet - probably a lot quieter than your existing machine, from what you say. Here at work we've got an external hard drive here that's louder than our Mac Pro (and the drive ain't exactly what you'd call noisy...).

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